Method and process for producing a water-resistant, mechanically stable form of torrefied biomass

Abstract

Disclosed herein is a binder-free product and process for making the product. The product is a mechanically stable, water resistant torrefied biomass product that does not comprise an extrinsic binder additive. The product is made using a combination of appropriate pre-treatment steps and compressing the conditioned biomass feedstock into a thermally managed compaction device comprising at least one modified die. The modified die allows for differential cooling/heating modifications so as to control the temperature near the entrance to the compaction device and passing the formed torrefied biomass into a post-formation curing zone.

We claim: 
     
       1. A product, comprising binder-free, compacted torrefied biomass having an average mass density of at least about 1.1 g/cm 3  to about 1.3 g/cm 3  and from about 20 wt % to about 35 wt % water based on the weight of the product after submersion for about 24 hours in water at ambient conditions as compared to the weight of the product prior to submersion. 
     
     
       2. The product of  claim 1  consisting essentially of compacted torrefied biomass. 
     
     
       3. The product of  claim 1  wherein the mass density ranges from about 1.1 g/cm 3  to about 1.2 g/cm 3 . 
     
     
       4. The product of  claim 1  wherein the product has a water uptake ranging from about 25 wt % to about 35 wt %. 
     
     
       5. The product of  claim 1  wherein the product has a friability index ranging from about 13 to about 50. 
     
     
       6. A method for making binder-free, compacted torrefied biomass, comprising:
 milling uncompacted torrefied biomass to have an average particle size of about 0.1 mm to less than about 10 mm; 
 sieving the uncompacted torrefied biomass; 
 conditioning the uncompacted torrefied biomass to increase its moisture content to about 5% to about 15%; 
 compacting the uncompacted torrefied biomass in a compaction device without an extrinsic binder additive, wherein the compaction device comprises at least one die modified to comprise an opening defining an inlet and an outlet, and wherein the inlet is configured to have a temperature of from about 80° C. to about 140° C. and the outlet is configured to have a temperature of from about 120° C. to about 140° C.; and 
 curing the compacted torrefied biomass in a post-compaction device to produce the compacted torrefied biomass having an average mass density of at least about 1.1 g/cm 3  to about 1.3 g/cm 3  and that absorbs from about 20 wt % to about 35 wt % water based on the weight of the compacted torrefied biomass after submersion for about 24 hours in water having a temperature of about 25° C. and at ambient pressure as compared to the weight of the compacted torrefied biomass prior to submersion. 
 
     
     
       7. The method of  claim 6  wherein the uncompacted torrefied biomass is sized to have an average particle size of less than about 2 mm. 
     
     
       8. The method of  claim 6  wherein the compaction device is a cuber. 
     
     
       9. The method of  claim 8  wherein the cuber is fitted with at least one die that is modified to comprise an opening defining an inlet having a temperature ranging from about 80° C. to 140° C., and an outlet having a temperature ranging from about 120° C. to about 140° C. 
     
     
       10. The method of  claim 6  wherein the compaction device is operated to provide residence time of the biomass as it passes through the die modified to comprise the opening with the residence time ranging from about 5 seconds to about 15 seconds. 
     
     
       11. The method of  claim 8  wherein the cuber is operated to provide a biomass residence time ranging from about 5 seconds to about 15 seconds as it passes through the die modified to comprise the opening. 
     
     
       12. The method of  claim 6  wherein curing comprises passing collected compacted torrefied biomass through an oven set at a temperature of from about 80° C. to about 150° C. and is heated in the oven for less than about 5 minutes. 
     
     
       13. The method of  claim 12  wherein the oven is selected from a convection oven, a radiant oven, or a microwave oven. 
     
     
       14. The method of  claim 13  wherein the compacted torrefied biomass is heated in the microwave oven for about 10 second to about 30 seconds. 
     
     
       15. A system, comprising:
 a first stabilizer/conditioner component configured to receive a torrefied biomass feedstock and apply a liquid to the torrefied biomass; 
 a compaction device configured to receive the torrefied biomass feedstock from the first stabilizer/conditioner and capable of compacting torrefied biomass to have a mass density greater than that of the torrefied biomass feedstock, wherein the compaction device comprises at least one die modified to comprise an opening defining an inlet and an outlet, and wherein the inlet is configured to have a temperature of about 80° C. to about 140° C.; and 
 a second stabilizer/conditioner component configured to receive the compacted torrefied biomass and thermally cure the compacted torrefied biomass. 
 
     
     
       16. The system of  claim 15  wherein the first stabilizer/conditioner component comprises a milling component and a sieving component. 
     
     
       17. The system of  claim 15  wherein the second stabilizer/conditioner component is a conveyor oven selected from a convection oven, a radiant oven, or a microwave oven.